The present invention relates to a technique for live migration of virtual machines among servers located at different network points.
As the amount of communication traffic on the Internet has been increasing, the amount of power consumption in terms of entire networking has also been growing continuously. Meanwhile, the significance of power saving is becoming higher in the efforts of solving the global warming issue including suppression of carbon dioxide emissions. Although a certain level of power saving has been accomplished in individual data centers and network nodes by using conventional techniques, it is of critical importance at present that each data center and a wide area network (WAN) should be arranged to work cooperatively for achieving more effective power saving. One of the reasons is that the removal of all the loads of particular communication traffic flowing between a data center and users or other servers makes it allowable to shut down power to relevant devices of the data center and network nodes associated therewith that are provided for the particular communication traffic.
As a conventional technique for reducing power consumption in server operation, there is known a method wherein, when the rate of server utilization has decreased, processing operations distributed among plural servers are collectively shifted to a particular one or particular ones of the servers, and the remaining servers thus freed from loads are powered off. For collective shifting of processing operations in such a case as mentioned above, it is common practice to virtualize the servers so that normal processing operations are performed on virtual machines (VMs). Then, in units of VMs, server-to-server migration thereof (movement/transfer) is carried out whenever appropriate. Migration of a VM being active in processing from the current server thereof to another server is referred to as live migration. Server virtualization techniques such as Xen and VMware (registered trademarks) are available at present. A live migration technique regarding the Xen is described in Non-patent Document 1 indicated below, and a live migration technique regarding the VMware, i.e., a technique of VMotion is described in Non-patent Document 2 indicated below.
In live migration, it is required to prevent the occurrence of an adverse effect such as an interruption of communication or a delay of response in each application running on the VM concerned. On each server in a data center, there are carried out various applications including realtime applications such as online games and conference systems. To circumvent an adverse effect on these realtime applications, it is necessary to minimize a downtime, i.e., a period of time the execution of applications is suspended during migration. In the Non-patent Document 1, it has been reported that a VM being active in running an online game named Quake 3 was successfully migrated with a total downtime of 60 ms, thus providing effectively seamless migration from a user's point of view.
In Patent Document 1 indicated below, there is disclosed a technique for shortening a period of time from the moment when a VM before migration is stopped until the moment when the VM after migration is started in the case of live migration on a LAN.
In Non-patent Document 3 indicated below, there is described a method for implementing VM migration over a wide area. In accordance with the method described in the Non-patent Document 3, even in cases where a VM is migrated to any location on an IP network, communication can be continued by using Mobile IP. Further, Patent Document 2 indicated below discloses a method wherein distant data centers are connected through a Level-2 (L2) path based on encapsulation using the Internet Protocol, thereby enabling such an operation as live migration.